1. Field of the Invention
The present invention relates to surgical lead bodies which provide electrical stimulation to nerve tissue of a patient. More particularly, but without restriction to the particular use which is shown and described, the present invention relates to a surgical lead body having a minimum cross section such that the surgical lead body may be percutaneously implanted through a modified Tuohy needle having an oblong shaped opening.
2. Description of the Related Art
It is known that nerve tissue stimulation is used to treat numerous neurological disorders, including, but not limited to, cerebral palsy, multiple sclerosis, amyotrophic lateral sclerosis, dystonia, and torticollis. It is further known that nerve tissue stimulation is useful to treat intractable malignant and nonmalignant pain. Stimulation of nerve tissue of the spinal cord, for example, is often accomplished through implanted medical leads in the epidural space of the spinal cavity. The implanted lead defines a lead body which includes neural stimulation electrodes that conduct electrical stimulation signals from a stimulation source, such as implantable pulse generators, to targeted nerve fibers in the epidural space. These medical leads may be percutaneous lead bodies which have a cylindrical shape with cylindrical electrodes spaced along the body of the lead. Also, the medical leads may be surgical lead bodies with electrodes spaced in an array on a paddle-type lead body.
As conventional, the percutaneous lead body is introduced into the epidural space of the spinal cord using a needle and stylet. The needle (commonly referred to as a Tuohy needle) and stylet are inserted into the targeted spinal column area between adjacent vertebrae until the tip of the needle and stylet are positioned into the epidural space. The stylet is withdrawn and a percutaneous lead body is inserted through the opening or lumen of the needle into the epidural space and positioned at the targeted stimulation area. The needle is then withdrawn leaving the percutaneous lead body in the desired stimulation position. Drawbacks encountered with known percutaneous lead bodies include migration or movement of the lead body after it is implanted. In addition, the cylindrical shape of the electrode in the percutaneous lead body generates omni-directional stimulation instead of one-directional, focused stimulation.
The surgical lead body which is typically a paddle-type lead body often has a rectangular, flat cross-section. Spaced in an array on one side of the paddle are the electrodes. The array of electrodes provides better stimulation coverage of the targeted nerve tissue than a percutaneous lead body. In contrast to the percutaneous lead body, however, the surgical lead body is surgically implanted into the epidural space. This requires a physician to perform a laminotomy, laminectomy, or similar procedure, prior to the insertion of the surgical lead into the epidural space. Once implanted, the surgical lead having the flat, rectangular shape is generally more stable than a percutaneous lead and provides one-directional stimulation—stimulation more focused than a percutaneous lead body. A drawback with the surgical lead body, however, is the performance of a laminotomy or similar surgical procedure. Anesthesiologists who frequently provide the nerve tissue stimulation for a patient are often prevented from using the surgical lead body as the laminotomy procedure is generally outside the scope of their practice.